Does keyframe 0 have a "special" use case in blender?
'0' may be the starting point for programming, but blender is aimed at artists, who may well not have any programming knowledge, for which a zero-starting counting system may not make any sense. Of course, the artist may have programming knowledge and be aware of zero-starting counting, but it is not presumed.

Frame '0' has no significance or importance over any other frame. If users choose to consistently do something with that '0' frame then that would be an individual choice, and not a standard convention (as far as I'm aware).